The new ordered vacancy compound Ag3In5Te9 was synthesized by the melt and annealing technique and its structure was refined from X-ray powder diffraction pattern using the Rietveld method. The title compound crystallizes in the tetragonal space group P 2c (Nº 112), with a = 6.3453(2) Å, c = 12.5754(7) Å, V = 506.32(4) Å3. The refinement of 23 instrumental and structural parameters led to Rp = 5.4%, Rwp = 5.8%, Rexp = 5.1 %, S = 1.1. This ternary compound is isostructural with Cu3In5Te9 and have a defect adamantane structure.